I ordered Cusco RS lsd and 3.9 final drive gears.. still got a few weeks to wait until they arrive.

I got bored at work today and created this graph with my dyno chart and gear ratio, the graph shows the chracteristics difference between the two gears.

I thought there could be someone who would want to see the difference in accel between 3.5 and 3.9 gears on a graph, so here we go

 

The 3.9 certainly makes a difference in accelaration, but I don't know if it is really that much more significant from a dead stop because you have to shift sooner as you get to redline faster. On the other hand when the car is already in motion it does accelerate quicker. Interesting chart.

BTW I have the 3.9 gears and I think it is the best bang for the buck mod for the 350Z.

 

What do you guys think, a boosted Z with the Twin set up from APS would be with the 3.9. I mean i dont think it would grab tracktion.

 

With that high of a gearing, your 1st gear would probably be useless.

 

You want higher gearing if you have a high amount of boost

If you're NA 3.9 will do wonders.....if you're boosted you'll be shifting too fast

 

3.9 isn't that bad when you think abot it. i had a chevelle that had 4.11's. that is a common setup up in many muscle cars. i have a few friends that run 4.32 in their novas. those cars take off.

on another note. your gas mileage will go down a bit.

 

you can't really compare final drives from different cars unless they have similar transmission gear ratios

it's possible to have a car with a 4.11 be way weaker overall in each gear than a car with a 3.3 with shorter transmission gears

it partly depends on how many gears the transmission has

 

Generally the 3.9 is a NA mod. Not the best mod for most FI applications.

 

whether from a roll or a dead stop, the 3.9 gears are equally effective...its a static change you are making, it is not rpm dependant. Everything will happen ~10% quicker.

Works great for a NA car, especially one with a raised rev limiter. Works REALLY well on a supercharger like a Vortech, which makes all its power up top. On the twin setups, might not be the best mod as the boost tends to come in fairly quickly due to the bigger displacement and compression these motors have.

 

My question is are you guys considering this mod for road racing or 1/4 mile racing? I've done the gear ratio calculations and the stock 3.5 gear is actually more ideal in a 1/4 mile race when you consider ending/beginning torque on each successive shift. Deeper gears will ALWAYS give a greater sensation of acceleration, but when timed, it may not be an advantage.

 

So let me get this straight. Judging by your chart, a Z with the stock 3.5 final drive can hit 295km/h where as the 3.9 can only hit around 270km/h. This is of course with the speed limiter removed.

 

Yes that is correct

 

True ! back in the day, I had a 383ci, 335hp Roadrunner w/3.55 diff. Totally stock 14.27 qtr mi; Swopped the rear end diff for a 3.91, qtr times dropped to 13.88 and gass mileage was terrible, but it sure was fun.

 

Because, i used to have a 04 330ci, boosting 8psi on the ESS kit, with my 3.68 i had no traction first gear. But i had 9.5 in the back for rubber grip. I thought with maybe 20x10 in the back. Its for road use only i don't track my cars. Hmm iam sorry to sound like a new its i honestly dont know **** bout the Z. I don't even have one, but I am buying one. It was that or a M3. But with the money i save from not buying tha M3 i can get a second condo to rent out and make some more money that way.

 

I'm gona get flammed for this but...what do the numbers on the left side (vertical) column represent?

 

the torque that's multiplied from the engine thru the transmission to the wheels

 

BTW, I redid the graph so it reads MPH instead of KM/H

 

I've also read that swapping to the 3.9's does not increase your 1/4 time at all. It's best suited for racing such as auto-x or circuit racing.

 

3.9 can improve your 1/4 time as long as you shift fast because usually by the end of the 1/4 you will be in 5th gear where are with a oem FD you will be in 4th

 

have the central 20 units been selling? Im asking because I know there alot cheaper then the other unit (forgot the brand).